Pregnancy And Medicines (1.2) Flashcards
A) What are teratogens?
B) What are some developmental anomalies
C) What is an abnormality?
D) How does the teratogenic mechanism work?
A) Teratogens
- Agents that act irreversibly to alter growth, structure or function, of the developing embryo or foetus
B) Developmental anomolies
- Birth defects, congential malformations, or congenital or structural abornamilities
- E.g. spina bifida, congenital heart defects, cystic fibrosis, haemophilia
C) Abnormality
- Present at conception or occurs before the end of pregnancy and is diagnosed by 6 years of age
D)
- Mechanism is unclear, may be due to effect of drug on foetus and/or a consequence of indirect physiological changes in the mother or foetus
Describe the exposure of teratogens in the;
A) pre-embryonic/implantation stage
B) embryonic stage
C) foetal stage/foetogenesis
A) days 14 to 28 of the cycle/ days 0-17 post conception
- All or nothing response = clinical miscarriage or if pregnancy continues the rate of birth defect is comparable to a non-exposed embryo
B) weeks 4-10 after last menstrual period (LMP) or day 18-55 post conception
- Most critical part of development (organogenesis)
- Exposures may cause structural birth defects
C) from 11 weeks until term or day 56 to term
- Not a high risk-time for birth defects
- Exposures may affect or disrupt normally formed organs in a number of different ways
Why should drugs like alcohol be avoided even after the first trisemester?
Brain and nervous system continue to grow and develop through pregnancy
What are some principles of teratology? (study of abnormalities of physiological development)
- Critical periods of development
- Species susceptibility
- Dose influence (dose, route of administration, maternal pahrmacokinetics,clearance volume, drug properties, duration)
- Genetic and other individual factors
In terms of teratology, what are lower risk drugs? Provide some examples
Drug groups that carry minimal risk of adverse effects at normal therapeutic doses
- Antacids
- Inhaled asthma medications
- Paracetamol
- Penicillins and cephalosporins
- Laxatives
In terms of teratology, what are some exmaples of higher risk drugs?
- ACE inhibitors
- Anticonvulsants
- Ehtanol
- Retinoids
- Estrogens
- Warfarin
What is the most common cause of miscarriages?
Genetics (between 15-20 % of all pregnancies may end in spontaneous miscarriage)
How are drugs categorised in Australia? Is the catergorisation system hierarchal?
- Drugs are categorised by (A, B1, B2,B3, C, D, or X)
- Generally A is the safest while the X is the least safe
- No the system is not hierarchal
- Human data is lacking or inadequate for drugs in the B1, B2 and B3 categories
- Subcategorisation of the B category is based on animal data
- B category does not imply greater safety than a C category
What are some references and resources that can be used?
- TGA mediicines in pregnanacy database
- AMH and eTG
- KEMH (the hub)
What are some counselling considerations when a patient asks for medicines when pregnant?
- When in the pregnancy
- Pre-existing conditions eg diabetes
- Acute medical condition eg UTI
- New pregnancy related condition eg hyperemesis
- Maternal concern often overstimated as foetus is unintended recipient (mothers may become non-adherent ==> puts mother and baby at risk)
Counselling: Questions to Ask
- Prospective or retrospective exposure
- Identify drug, dose frequency, route and duration of exposure
- How many weeks pregnant when started drug
- How many weeks now
- Taken the drug in previous pregnancy?
- Family history of malformations?
In terms of the drug choice, what are some possible ways to minimise risks?
- Try non-drug treatments first
- Avoid first trisemester unless clinically indicated
- Use as few drugs as possible
- Use the lowest effective dose for shortest period
- Use safest drugs in group
- Use older drugs without evidence of harm
- Avoid newer drugs with little information
